1. Field
One embodiment of the present invention relates to a disk drive that uses a disk medium on which servo data and servo management data are recorded.
2. Description of the Related Art
In most disk drives, a representative example of which is a hard disk drive, the positioning of the heads is controlled in accordance with the servo data (servo pattern) that is recorded on a disk-shaped medium (disk medium), i.e., a data-recording medium. That is, the heads are moved to target positions (i.e., target tracks or target cylinders) on the disk medium, in accordance with the servo data the heads have read.
The servo data has been recorded on the disk medium in the servo-writing step performed in manufacturing the disk drive. In the servo-writing step, an apparatus called servo-track writer (STW) writes the servo data on the disk media before or after the disks are incorporated into the disk drive.
In the step of writing servo data on a disk medium, writing errors may be generated. In such a case, the STW keeps writing the servo data if the errors fall within a tolerable range. The STW generates information (hereinafter referred to as “servo-write management information”) about the writing errors and the parts of the medium where the writing errors have occurred. The STW writes the servo-write management information on the disk medium. This information is defect information that contains data items representing the parts of the medium where the writing errors have occurred and data items representing the other parts of the medium on which data may be written instead. In most cases, these data items are address codes of the servo sectors and servo tracks.
The servo-write management information is useful in inspecting the troubles the disk drive after the disk drive has been shipped. A system has been proposed, in which the servo-write management information (STW management information) is recorded in the sector-number area (i.e., sector-address area) in which to write the servo data. (See, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-45132.) In this system, however, the sector-number area increases in proportion to the number of servo sectors in which servo-write management is recorded.
A system has been proposed, in which the servo burst signals (i.e., servo burst patterns) contained in the servo data are used to save the storage area of the servo sectors. (See, for example, Jpn. Pat. Appln. KOKAI Publication No. 2002-516449.) In this system, however, no measures are taken in connection with the recording of servo-write management information. An increase in the storage area of servo sectors cannot be suppressed at all.
If the servo-write management information is recorded on the disk medium, together with the servo data, it will indeed help to inspect the disk drive in the event of errors. However, increasing number of servo data, in which the servo-write management information is buried will be one of the factors that prevent an increase in the density in which the user data is recorded.